<template>
  <div>
    <TransitionGroup name="list" tag="div" class="container">
      <div
          class="item"
          v-for="(item, i) in drag.list"
          :key="item.id"
          :draggable="true"
          @dragstart="dragstart($event, i)"
          @dragenter="dragenter($event, i)"
          @dragend="dragend"
          @dragover="dragover"
      >
        {{ item.name }}
      </div>
    </TransitionGroup>
  </div>
</template>
<script setup>
import {reactive} from 'vue';

const drag = reactive({
  list: [
    {name: 'a', id: 1},
    {name: 'b', id: 2},
    {name: 'c', id: 3},
    {name: 'd', id: 4},
    {name: 'e', id: 5}
  ]
});

let dragIndex = 0;

function dragstart(e, index) {
  e.stopPropagation();
  dragIndex = index;
  setTimeout(() => {
    e.target.classList.add('moveing');
  }, 0);
}

function dragenter(e, index) {
  e.preventDefault();
  // 拖拽到原位置时不触发
  if (dragIndex !== index) {
    const source = drag.list[dragIndex];
    drag.list.splice(dragIndex, 1);
    drag.list.splice(index, 0, source);

    // 更新节点位置
    dragIndex = index;
  }
}

function dragover(e) {
  e.preventDefault();
  e.dataTransfer.dropEffect = 'move';
}

function dragend(e) {
  e.target.classList.remove('moveing');
}
</script>

<style scoped>
.item {
  width: 150px;
  height: 150px;
  line-height: 40px;
  background-color: skyblue;
  text-align: center;
  margin: 10px;
  color: #fff;
  font-size: 18px;
}

.container {
  position: relative;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  width: 540px;
}

.moveing {
  opacity: 0;
}

.list-move,
.list-enter-active,
.list-leave-active {
  transition: all 0.2s ease;
}
</style>